If you get denied for a major credit card, try applying for a retail store credit card. They have a reputation for approving applicants with bad or limited credit history. Still no luck? Consider getting a secured credit card which requires you to make a security deposit to get a credit limit. In some ways, a secured credit card is more useful than a retail credit card because it can be used in more places.
Next, estimate your monthly spending habits for other expenses such as gas, groceries and entertainment. Create a limit, based on your income, of what you can spend in each of the different categories of expenses. For example, if you tend to spend $400 a month on groceries, try to stick to $300 a month on groceries by making changes like buying generic brands, using coupons, and resisting impulse purchases.